Photographic element containing silver salt-forming bleachable filter dyes



Sept. 27, 1955 A. H. HERZ ET AL PHOTOGRAPHIC ELEMENT CONTAINING SILVER SALT-FORMING BLEACHABLE FILTER DYES Filed NOV. 14, 1951 F1 q 1 GELA TIN LA YER CONTAINING 81L v51? 12 ,x SALT or THIOBARBITURIC ACID DYE l1 -EMULsIoN 10 ,i suPP RT SUPPORT PM E. BLUE SENSITIVE EMULSION I/EMULSION ,1 l0 \g/ 17 ANTIHALA TION LAYER CONTAINING SILVER SALT OF THIOBARBITURIC ACID DYE ARTHUR H. HERZ GRAFTON H. KEYES INVENTOR.

ATTORNEYS United States Patent H PHOTOGRAPHIC ELEMENT CONTAINING SILVER SALT-FORMING BLEACHABLE FILTER DYES Arthur H. Herz and Grafton H. Keyes, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application November 14, 1951, Serial No. 256,240

7 Claims. (Cl. 95-8) This invention relates to improvements in photographic elements and more particularly in photographic elements having light screening substances therein.

It is known that photographic elements require, for many purposes, light screening substances incorporated therein. Such a light screening substance may be in a layer overlying a light sensitive emulsion or overlying two or more light sensitive emulsions; or it may be in a light sensitive emulsion for the purpose of modifying a light record in such emulsion or of protecting an underlying light sensitive emulsion or emulsions from the action of light of wave length absorbed by such light screening substance; or it may be in a layer not containing a light sensitive substance but arranged between two light sensitive emulsions; or it may be in a layer serving as a backing on an element having one or more light sensitive emulsions (for example, to reduce halation).

In particular, light screening substances are often required (a) in overcoatings upon photographic elements to protect the light sensitive emulsion or emulsions from the action of light which it is not desired to record, e. g. ultra-violet light in the case of still or moving pictures, especially color pictures, (b) in layers arranged between differentially color-sensitized emulsions, e. g. to protect redand green-sensitized emulsions from the action of blue light and (c) in backings, forming the so-called anti-halation layers, on either side of a transparent support carrying the light-sensitive emulsion or emulsions.

I In most cases, and especially when the element contains a color-sensitized emulsion or color-sensitized emulsions, it is particularly desirable to employ light-screening substances which do not affect the general sensitivity or the color sensitivity of light-sensitive emulsions with which they may come into contact. It is also particularly desirable to employ light-screening substances which do not substantially diffuse from the layers or coatings in which they are incorporated, either during the manufacture of the element or on keeping it or in photographically processing it. Finally, it is generally necessary to employ light-screening substances which can readily be rendered ineffective, i. e. decolorised or destroyed and removed, prior to or during or after photographic processing; for many purposes it is particularly convenient to employ light-screening substances which are rendered ineffective by one of the photographic baths employed in processing the element after exposure, e. g. a photographic developing bath or fixing bath or a silver-oxidizing (including silver-removing) bath. For example, in an element which is to be processed by reversal, it is often convenient to employ a light screening substance which is rendered ineffective by the developer employed to develop the latent image or images to silver since exposure to light of the residual light sensitive emulsion or emulsions may thereby be facilitated. This is particularly the case when, in making color photographs, several differentially color-sensitized emulsions, constituted, for example, by silver halide, such as silver bromide dispersed in gelatin, collodion or other colloid, are coated on one 2,719,088 Patented Sept. 27, 1955 or both sides of a support, for example, in inseparablysuperimposed layers. Such differentially color-sensitized emulsions have to be processed to different colors and to facilitate the differential color-processing, methods involving selective exposure of light sensitive images, in the layers may be employed. Such selective re-exposure, e. g. of silver halide remaining undeveloped in development of the latent images formed in silver halide emul sion layers (residual silver halide) is often facilitated if the light-screening substance which was present during the original exposure is decolorized or removed in the developing bath employed to develop the latent images to silver. Any of the elements referred to above may be such that one or more of the emulsions contain coupling components, e. g. those described in French Patent 834,371, granted August 16, 1938.

Numerous substances have been employed as lightscreening substances for the purposes indicated above. (Many of these are known yellow dyes butit has proved extremely difiicult to find dyes having the combination of qualities desired.) Many are not resistant to diffusion and wander rather freely from the layer in which it is intended that they should remain; many adversely affect the sensitivity of light sensitive emulsions with which they come into contact (a number of these reduce the general sensitivity or some specific color sensitivity thereof, but others of them may even impart an additional and unwanted specific color sensitivity thereto).

Peterson U. S. Patent 2,266,441, describes the use as filter dyes of silver salts of various dyes derived from thiobarbituric acid. Most of these are azo dyes and are not bleached during normal photographic processing; hence contain solubilizing groups to permit removal of the dye by Washing out during or after the hypo bath. Actual practice has shown the difiiculty of preparing silver salt-forming dyes or dye components which on the one hand are completely nondiffusing in the form of their silver salts, while on the other hand, can be readily washed out of the gelatin after the silver has been removed.

We have found a class of dyes which, in the form of their silver salts, are dischargeable in the processing solutions and do not need solubilizing groups to make them removable by washing; hence are more diffusion resistant. The dyes which we propose to use have the following tautomeric formulas:

where R=hydrogen, phenyl or alkyl Y=carbon or nitrogen Z=the atoms necessary to complete a 3-pyrrole or 1- 1,2,3,4) -tetrahydroquinoline ring.

In the drawing the figures are enlarged sectional views of photographic elements showing overcoating, filter and antihalation layers according to our invention.

The general formula indicates that our compounds may be depicted in two electromeric forms.

The following examples illustrate compounds which may be used according to our invention:

5-'y{ 1-(1,2,3,4-tetrahydroquinolyl) ]-allylidene}-2-thiobarbituric acid.

( HNC O E 2,5 -dimethyl- 1-phenyl-3-pyrryl) -methylene] -2-thiobarbituric acid.

I (IJ=CH CO HaC CH: N

5 [(2,5 dimethyl-1-phenyl-3-pyrryl)-methylene]-1- phenyl-Z-thiobarbituric acid.

( HN-OO 5:? (3:011 HsCr-NCO H30 N CH:

5 [(2,5 dimethyl 1-phenyl-3-pyrryl)-methylene]-1- ethyl-Z-thiobarbituric acid.

These compounds are prepared as follows:

( 1) 5 {'y[1 (1,2,3,4 tetrahydroquinolyD] allylidene}- 2 thiobarbituric acid A mixture of 1.45 gram (1 mole) of 2-thiobarbituric acid, 1.9 gram (1 mole) of 1-18-formylvinyl-1,2,3,4-tetrahydroquinoline, 50 cc. of ethyl alcohol and 2 drops of piperidine was refluxed for two hours. The dye separated on cooling. The crude dye wasrepurified by repeated recrystallization from methyl alcohol and was obtained as reddish crystals having a melting point of 283- 85 C. with decomposition.

The preparation of l-fl-forrnylvinyl-l,2,3,4-tetrahydroquinoline is described by Dieterle et al. in Zeit. fur wiss. phot., vol. 36, p. 68 (1937).

(3) 5 [(2,5 dimethyl 1 phenyl-3-pyrryl)-methylene]- 1-phenyZ-Z-zhiobarbituric acid formed by dissolving 9.2 g. of sodium in 150 cc. of absolute ethyl alcohol, was added 64 g. (1 mole+ 100% excess) of diethylmalonate and then 30.4 g. (1 mole of phenylthiourea). The mixture was stirred mechanically and heated on a steam bath for a seven-hour period. Heating at this temperature without stirring was then continued for a further three-day period. After adding 150 cc. of water, most of the alcohol was removed by distillation under slightly reduced pressure. The residue was then poured into 500 cc. of cold water and the solution filtered. The product separated on acidification of this filtrate. The yield of crude product was 40 g. of theory. A sample was purified by recrystallization from methyl alcohol and was obtained as nearly colorless crystals having a melting point of 217-19 C. with decomposition.

Compound 2 was prepared similarly to compound 3, using 2,5 dimethyl-1-phenylpyrrole-3-aldehyde and thioa barbituric acid.

Compound 4 was prepared as follows:

A mixture of 1.7 g. (1 mole) of 1-ethyl-2-thiobarbituric acid, 2 g. (1 mole) of 2,5-dimethyl-1-phenylpyrrole-3-aldehyde and 50 ml. of absolute ethyl alcohol were heated together under reflux for 15 minutes. The yield of well washed dye was 86% of theory. After two recrystallizations the dye was obtained as brownish-yellow crystals in 64% yield, M. P. 246-248 C. with decomposition.

The 1-ethyl-2-thiobarbituric acid used in above example was prepared as follows:

18.4 g. (l mole+% excess) of sodium was dissolved in 300 ml. of absolute ethyl alcohol; after cooling this solution to about 60, 128 g. (1 mole+100% excess) of ethyl malonate was added with mechanical stirring, followed by 41.6 g. (1 mole) of ethyl-thiourea. The reaction mixture was heated at steam-bath temperature with stirring for a 6-hour period and without stirring for a further 72 hours. 300 ml. of cold water was then added to the mixture and most of the alcohol was removed by distillation. The residue was treated with 1 liter of cold water and the mixture filtered. This filtrate was then acidified. The product which separated was collected on filter, washed well with water and dried. It was used without further purification. The yield was 89% of theory.

The following examples illustrate the formation of filter layer with the silver salts of dyes according to our invention:

Example 1 2 1 0- mols of 5-'y{-[1-(1,2,3,4-tetrahydroquinolyl) 1- allylidene}-2-thiobarbituric acid was dissolved in 5 cc. of pyridine and added to 4 g. of gelatine in 50 cc. of water containing 4X10- mols of silver nitrate. The resulting gelatin-dispersion of the dye was set, shredded and washed free of pyridine. It was then remelted with the addition of 6 g. of'gelatine, giving a volume of 0.2 liter. The pH was adjusted to 6.5 with a sodium hydroxide solution. KCl was added to eliminate excess silver salts. It is essential that the dispersion should contain neither excess silver or dye over that necessary to form the silver salt of the dye. This occurs at a silverion concentration of about 10- molar. The resulting dispersion has its maximum absorption at 430 mu. It was coated on film base and over-coated with a silver-bromoiodide emulsion.

Although the dye, when added to the emulsion directly, was shown to be an active orthochromatic sensitizer with a maximum sensitivity at 500 m the above emulsion coating did not exhibit any speed, contrast or sensitization changes other than the slight speed loss due to the lack of reflection in the region of emulsion sensitivity, which indicates that the silver salt of the dye did not diffuse to the adjacent emulsion.

2,719;oss

Example 2 One-tenth gram of 5- (2,5-dimethyl-l-phenyl 3-pyrryl)- methylene]-1-phenyl-2-thiobarbituric acid was dissolved by heating in 2 cc. of 1% NaOH, cc. of methyl alcohol and 5 cc. of water. This dye solution was added to an aqueous gelatin dispersion containing 10 g. of gelatin and 5 cc. of 0.1 N AgNOa. After formation of the silver salt of the dye, enough water was added to give 0.2 liter of a gelatin dispersion. The pH was adjusted to 6.5 with sodium hydroxide and KCl was added to eliminate excess silver salts. The maximum absorption of this dye dispersion is at 450 mu.

Another dispersion of the dye but this time without addition of silver, was prepared just as above.

Upon overcoating these dye-gelatine dispersions with an unsensitized bromoiodide emulsion and developing and fixing them in ordinary photographic processing solutions, it was found that the emulsion coated over the silver-saltcontaining layer had the same speed and other charac teristics as the emulsion coated over a plain gelatin control, whereas the emulsion coated over the gelatin-containing free dye showed a speed decrease of about 70% in the blue and green spectral regions.

This demonstrates the diiference in difiusion between the free dye and the silver salt of the dye.

Example 3 This example will demonstrate the use of silver salt forming bleachable dyes as an integral part of the emul- $1011.

10- moles of 5-[(2,5-dimethyl-l-phenyl-S-pyrryl)- methylene] -2-thiobarbituric acid were dissolved in a boiling solution of 8 cc. of 1% sodium hydroxide, 60 cc. of methyl alcohol, and 10 cc. of water and then added slowly to 1 liter of solution containing cc, of 0.1 N silver nitrate. Upon completion of the addition, the pH was adjusted to 6.9 with sodium hydroxide and potassium bromide was added to eliminate excess silver salts.

This dye-gelatin dispersion was added to 5 liters of a bromoiodide emulsion and coated at a rate of 40 cc. per sq. ft. The resulting coating was processed as in Example 2. Sensitometric tests have shown that the emulsion characteristics were not altered by the addition of the silver salt of the dye except for an approximately 50% speed loss which was accounted for by the filter action of the dye itself.

It was noted that the dyes of Examples 2 and 3, although bleachable in ordinary developing solutions, were not affected by an acid fixing bath, whereas the silver salt of those dyes was completely discharged in such fixing bath.

Example 4 1.9 10- moles of 5-[(2,5-dimethyl-1-pheny1-3-pyrryl) methylene]-1-ethyl-2-thiobarbituric acid were dissolved in 1.2 cc. of alcoholic potassium hydroxide and 8 cc. of methyl alcohol. This solution was added to 67 cc. of 10% gelatin solution which had been adjusted to pH 10 with dilute NaOH. 8.0 cc. of 2 N sulfuric acid was added to 16.2 cc. of 0.1 N AgNO3, and then added to the gelatin solution containing the dye. At the end of the reaction, the pH was 4.58.

The gelatin dye solution was allowed to set, then shredded and washed with chilled water until free of excess salts.

Three coatings were made:

(1) A control of plain gelatin (2) The dispersion of the silver salt of the dye in gelatin, as described above (3) The free dye in gelatin having the same amount of dye per unit area as (2) All of these were overcoated with the same bromoiodide emulsion. (1) and (2) were practically identical in speed and contrast, showing that there was no diffusion 6 of dye into the emulsion layers. 3) had only about onehalf the speed of (l) and (2), with appreciable fog. (2) had adequate absorption for use as a filter layer, and bleached in normal photographic processing.

In the accompanying drawing, the various figures are enlarged sectional views of photographic elements having filter layers or antihalation layers made according to our invention. As shown in Figure 1, a support 10 of any suitable material such as cellulose nitrate, cellulose acetate, synthetic resinous material or opaquevmaterial such as paper is coated with an emulsion layer 11 and an overcoating layer of 12 containing the silver salt of a thiobarbituric acid derivative. made according to our invention.

Figure 2 illustrates a multilayer photographic element for color photography in which the support 10 is coated with sensitive layers 13, 14 and 15 which record, respectively, the red, green and blue regions of the spectrum. Between the emulsion layers 14 and 15, there is a filter layer l6 containing a yellow silver salt of a thiobarbituric acid derivative according to our invention. This filter layer serves a purpose well known in color photography of preventing exposure of a lower layer of the element by light which the filter'layer absorbs. The dye may also absorb light in other regions of the spectrum such as the 25 ultra-violet region.

Figure 3 represents a film having an antihalation layer containing a silver salt of a thiobarbituric acid derivative according to our invention. As shown therein, the support 10 carries anemulsion layer 11 on one side of an antihalation layer 17 containing a silver salt of a thiobarbituric acid derivative on the opposite side.

It will be understood that the examples included herein are illustrative only, and that our invention is to be taken as limited only by the scope of the appended claims.

We claim:

1. A photographic element comprising a support having thereon at least one silver halide emulsion layer and an unsensitized light absorbing layer free of silver halide containing a removable silver salt of a dye having the in which R is selected from the group consisting of alkyl and phenyl radicals, Z represents the atoms necessary to complete a l-phenyl-S-pyrrole ring, and n is from 0 to 2.

3. A photographic element comprising a support having thereon at least one silver halide emulsion layer and an unsensitized light absorbing layer free of silver halide containing a removable silver salt ofa dye having an electromericform of the formula:

I RNCO in which R is an alkyl radical, Z represents the atoms necessary to complete a 3-pyrrole ring, and n is from to 2.

4. A photographic element comprising a support havingthereon atleast one silver halide emulsion layer and an unsensitized light absorbing layer free of silver halide containing a removable silver salt of a dye having an electrorneric form of the formula:

HNC0 O I HN-CO CHr-CHi 5. A photographic element comprising a support having thereon at least one silver halide emulsion layer and an unsensitized light absorbing layer free of silver halide containing a removable silver salt of a dye having an electromeric form of the formula:

l 5:? +=CH HN-CO HaC CH3 N 6. A photographic element comprising a support having thereon at least one silver halide emulsion layer and an unsensitized light absorbing layer free of silver halide containing a removable silver salt of a dye having an ClCCtI'Ol'DCIiC form of the formula:

7. A photographic element comprising a support having thereon at least one silver halide emulsion layer and an unsensitized light absorbing layer free of silver halide containing a removable silver salt of a dye having an electromeric form of the formula:

U HgCZ-N-CO HaC CH3 N References Cited in the file of this patent UNITED STATES PATENTS 2,266,441 Peterson Dec. 16, 1941 FOREIGN PATENTS 524,500 Great Britain Aug. 8, 1940 524,558 Great Britain Aug. 8, 1940 529,440 Great Britain Nov. 21, 1940 867,411 France July 28, 1941 

1. A PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT HAVING THEREON AT LEAST ONE SILVER HALIDE EMULSION LAYER AND AN UNSENSITIZED LIGHT ABSORBING LAYER FREE OF SILVER HALIDE CONTAINING A REMOVABLE SILVER SALT OF A DYE HAVING THE TAUTOMERIC FORMULA: 